Structural basis and mechanism of autoregulation in 3-phosphoinositide-dependent Grp1 family Arf GTPase exchange factors
Structural basis and mechanism of autoregulation in 3-phosphoinositide-dependent Grp1 family Arf GTPase exchange factors
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DOI：
10.1016/j.molcel.2007.09.017
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发表时间：
2007-11-30
期刊：
影响因子：
16
通讯作者：
Lambright, David G.
中科院分区：
文献类型：
--
作者：
DiNitto, Jonathan P.;Delprato, Anna;Lambright, David G.
Arf GTP酶调节膜运输和肌动蛋白动力学。Grp 1、ARNO和Cytohesin-1组成了一个具有Sec 7-pleckstrin同源（PH）结构域串联的磷酸肌醇依赖性Arf GT3交换因子家族。在这里，我们报告Sec 7结构域的交换活性被PH结构域附近的保守元件有效地自抑制。Grp 1 Sec 7-PH串联体的晶体结构揭示了自抑制的假底物机制，其中结构域和C-末端两亲性螺旋之间的接头区域物理地阻断Arf GTP酶的开关区域的对接位点。任一元件内的突变导致部分或完全激活。自我抑制的关键决定因素也有贡献！胰岛素刺激的质膜募集。自抑制可以通过活性Arf 6与Grp 1的结合以及细胞粘连素-1中串联PKC位点的磷酸化而在很大程度上逆转。这些观察结果表明，Grp 1家族GEFs的自动调节机制，依赖于质膜招聘激活。
Arf GTPases regulate membrane trafficking and actin dynamics. Grp1, ARNO, and Cytohesin-1 comprise a family of phosphoinositide-dependent Arf GTPase exchange factors with a Sec7-pleckstrin homology (PH) domain tandem. Here, we report that the exchange activity of the Sec7 domain is potently autoinhibited by conserved elements proximal to the PH domain. The crystal structure of the Grp1 Sec7-PH tandem reveals a pseudosubstrate mechanism of autoinhibition in which the linker region between domains and a C-terminal amphipathic helix physically block the docking sites for the switch regions of Arf GTPases. Mutations within either element result in partial or complete activation. Critical determinants of autoinhibition also contribute! to insulin-stimulated plasma membrane recruitment. Autoinhibition can be largely reversed by binding of active Arf6 to Grp1 and by phosphorylation of tandem PKC sites in Cytohesin-1. These observations suggest that Grp1 family GEFs are autoregulated by mechanisms that depend on plasma membrane recruitment for activation.